Techniques of employing multiple antennas at both the transmitter and the receiver to enhance system performance, namely, the MIMO techniques, have been widely applied in various wireless communication systems of 3G/B3G/4G (3rd Generation/Beyond 3rd Generation/4th Generation). After extending traditional Shannon information theory to MIMO channels, there has been a tremendous enhancement in channel capacity, showing potential huge gain of the MIMO system. Before transmitting data from an antenna, it is required to perform MIMO precoding on the data. Precoding is a technology for preprocessing the signal to be transmitted using Channel-side Information at the Transmitter (CSIT) to obtain gain in a certain kind of performance. A Coordinated Multiple Points (COMP) transmission solution, capable of taking full advantage of the MIMO techniques to reduce interference in a wireless communication network and enhancing efficiency through close coordination of multiple access points signal transmission and reception, has become the key technical point in current OFDM (Orthogonal Frequency Division Multiplexing)-MIMO and has a strong prospect of application.
In a current cell wireless communication network, same frequency interference between adjacent cells is one of the most prominent factors causing performance declination, which in particular tends to hugely affect the performance of users at the edge of cells. Existing methods for reducing interference to users at the edge of adjacent cells are generally divided into three types, namely, interference randomization, interference elimination, and interference coordination; Wherein, the interference randomization technique is mainly used to randomize an interference signal and actually can not reduce interference; The interference elimination technique is intended to suppress interference by acquiring gain at a Mobile Station (MS) via signal processing techniques, which generally can only eliminate the major interference; While the interference coordination technique minimizes inter-cell interference by coordinating the precoding and resources among multiple cells.
The multi-BS MIMO technique is one of the aforementioned interference coordination techniques, and refers to a technique in which an MS in an OFDM/OFDMA (Orthogonal Frequency Division Multiple Access) system measures channel information between the MS itself and the serving BS, and feeds back a Precoding Matrix Indicator (PMI) which quantizes the channel information; measures channel information between the MS itself and a BS for an adjacent cell, and feeds back a restrained or recommended set of PMIs according to indication of the BS; and then a new Precoding Matrix for each MS is acquired by coordination among the BSs. This however can not eliminate interference among users at the border of adjacent cells.
Therefore, it is urgent to provide an improved method and device for coordinating downlink MIMO precoding among multiple BSs, to overcome the aforementioned defects.